1. Field of the Invention
This invention relates to a composite tubular body with at least one open end, at least one annular zone of fused quartz, and at least one annular zone of quartz glass, with the fused quartz produced essentially from quartz sands and the quartz glass from rock crystal or synthetic silicon dioxide. This invention also relates to a method of manufacturing a composite tubular body of the type described.
2. Discussion of Prior Art
Composite tubular bodies that are built up of separately manufactured parts are known (Heraeus Quarzschmelze Prospectus Q-B 3/113 [1979]). They consist of parts manufactured from fused quartz by the known process disclosed in German Pat. No. 543 957 along with at least one separately manufactured part of quartz glass produced from rock crystal or synthetic silicon dioxide. Since the fused quartz is obtained mainly from quartz sands, it is not completely pure and contains a larger or smaller amount of tiny air bubbles, which makes this fusion product opaque.
Furthermore, since these separately manufactured parts of fused quartz and quartz glass are fused together and finally tempered into a relaxation state, the fusion seam presents several problems. It has low mechanical strength. It prevents the walls from being as strong as desired. The length of the seam restricts the outer diameter of the tubular body to 300 mm. Manufacturing tolerances result in a bead along the site of the seam inside the tube that must, along with the seam itself, be ground down. This is detrimental to the glaze that develops inside the body as it is being manufactured, which is a special drawback when aggressive materials are employed, because they can penetrate into the resultingly porous wall. The necessity of fusing the parts together and then tempering and grinding the body make this method of manufacture very expensive.
It has become desirable, therefore, to provide a composite tubular body which is transparent as well as translucent, which has high mechanical strength and is not characterized by a fusion seam or bead at the site of a seam inside the tube.